1661156065 has 4 divisors (see below), whose sum is σ = 1993387284. Its totient is φ = 1328924848.

The previous prime is 1661156059. The next prime is 1661156083. The reversal of 1661156065 is 5606511661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5606511661 = 787 ⋅7123903.

It can be written as a sum of positive squares in 2 ways, for example, as 1230676561 + 430479504 = 35081^2 + 20748^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661156065 - 2²¹ = 1659058913 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 166115602 + ... + 166115611.

It is an arithmetic number, because the mean of its divisors is an integer number (498346821).

Almost surely, 2^1661156065 is an apocalyptic number.

It is an amenable number.

1661156065 is a deficient number, since it is larger than the sum of its proper divisors (332231219).

1661156065 is an equidigital number, since it uses as much as digits as its factorization.

1661156065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 332231218.

The product of its (nonzero) digits is 32400, while the sum is 37.

The square root of 1661156065 is about 40757.2823554270. The cubic root of 1661156065 is about 1184.3229505511.

The spelling of 1661156065 in words is "one billion, six hundred sixty-one million, one hundred fifty-six thousand, sixty-five".